This invention relates to a method of and an apparatus for determining the glossiness of a surface of a body, and more particularly to improvements in a method of and an apparatus for determining the glossiness of a surface of a body, suitable for use in measuring the surface quality of a steel sheet to control the same, wherein the glossiness based on visible feeling is classified and graded in accordance with the light reflection intensity distribution of the surface of the body.
Various methods of determining the glossiness of a surface of a body have heretofore been proposed which utilize light reflection measurement.
Such methods include:
(1) a method of measuring by specular surface glossiness, wherein the specular reflection intensity of a white light flux projected at a predetermined angle is measured;
(2) a method of measuring by contrasting glossiness, wherein a ratio between the main reflection intensity and the scattered reflection intensity of a white light projected at a predetermined angle is used; and
(3) a method of measuring by sharp glossiness, wherein another body is reflected by a surface and a blurred shape of the reflected image is visually inspected.
The method of measuring by specular surface glossiness is widely used in industry, but is inaccurate where the specular surface object has a low surface roughness. Furthermore, the method of measuring by contrasting glossiness is accurate for objects which are different in color from one another, but is less accurate with objects having nearly a specular surface. Further, the method of measuring by sharp glossiness is disadvantageous since no quantitative indication can be obtained.